Fly-ash recycling a potential in the UK

December 13, 2007 at 11:14 am

Fly-ash is produced from burning coal in power stations and consists of the small particles collected in the filters of the power stations’ chimneys. In the past, fly-ash was taken up by flue gases and released into the atmosphere, causing health and environmental problems. Currently, the majority of fly-ash is dumped in landfill sites but, with the associated financial and environmental costs, recycling the product has become increasingly important.

35% of fly-ash is recycled worldwide, with a variety of uses:

  • Replacing Portland cement in concrete
  • Engineering uses in constructing embankments
  • Stabilising soil for use in building roads
  • Making “flowable fill” used instead of compacted earth or granular flow
  • Using as a mineral filler for the voids in asphalt concrete
  • Making roller-compacted concrete for the construction of dams
  • Manufacturing bricks, although problems occur when the bricks come into contact with moisture and expand
  • Turning human waste into fertilizer

The UK sends some 66% of their fly-ash to landfill or uses it in lower value applications such as earthworks and road construction. This compares with only 5% in Germany, where the lion’s share is used for high value applications, such as concrete, grout and cement.

Thomas Duve, the chief executive of Evonik Power Minerals, thinks that the UK needs to monitor the quality of its ash better, as well as create a network with other European countries to exchange know-how and sell the product. By having proper control systems in place and possibly blending it, the fly-ash would become a far more marketable product in the construction industry. Mr Duve also suggested that the UK’s lower value fly-ash could be exported to those parts of Europe where it is in high demand for reprocessing, whilst importing better quality fly-ash into the UK from abroad to create demand.

Since January 2007, Evonik have been working to help UK power stations market their fly-ash. The company, which has helped over 50 German power stations market over 4 million tonnes of fly-ash per year, sees fly-ash not as a waste product but as a valuable by-product which can “help reduce the carbon footprint in this energy sector”, according to their marketing advisor, Hans Peter Ickemeyer. He explains that, because the production of products such as cement is so energy intensive, using concrete made from fly-ash for a third of the product could have a highly beneficial environmental impact.

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